That's the order the kids on the playground at Riverview Junior School in Kent, England, have just been given. The reason? They were getting too fit and happy.

Ah, just messing with you. The reason, of course, is the one that should send a shiver up your spine every time you hear it: It's for the safety of the children.

An interim co-head of the school explained to The Telegraph that more and more kids were joining in some chasing game. As a result, she said, "we have found the increasing numbers taking part has caused some injuries, including a fractured collarbone. We are concerned for the safety of the children (!!!) and need to stop this particular game until we can establish a safer way for them to play."

Perhaps the kids can be buckled into chairs and watch a DVD of children playing. That seems safer. Or maybe they can create online avatars to play the game for them, virtually. Heck, kill two birds with one stone and simply have them write personal essays about how fun the game would be, were they allowed to play it. That way, they're learning grammar, spelling and story structure. The hours will fly by!

Along with their childhood. Peter Gray is a psychology professor at Boston College and author of the book "Free to Learn." He has spent at least the past decade trying to convince educators that the traits they love most in their students — curiosity, creativity, problem-solving — are born when kids are playing.

"In play, kids are learning to be in control of their own lives," says Gray. "Unsupervised play is play that is controlled by the players themselves — the children. You learn all kinds of things in play, but the primary thing is to solve your own problems."

For instance, kids on a playground have to figure out: What should we do? How should we do it? Who makes the rules, the teams, the calls? How can I hold it together until it's my turn?

Those may seem like playground problems, but they echo in the classroom and beyond. When doing schoolwork, kids have to improvise and cope with frustration. Most of all, they have to focus. But after a child has played at being, say, a dog — "I must run on all fours and not talk, only bark" — it's a lot easier for her to transfer that kind of focus to doing a math problem. Certainly a lot easier than the other way around.

And if in Kent, as seems to be the case, the kids on the playground came up with a game so engaging that more and more kids wanted to play it, even if a few were getting knocked around, more power to them. They're working in a group, crafting rules, getting buy-in; those are actual management skills! They created something big, exciting and community-building, with only one small snag.